One must ask whether the UK and the US have the leadership, moral and strategic, to take immediate steps to halt Iran’s destructive meddling.

Aleppo has fallen, almost completely, to Syrian government forces in this past week, leaving not only rebel fighters but also tens of thousands of innocent civilians stranded in a bombed-out shell of that ancient city. Humanitarian intervention failed to prevent the disaster in the first place or the summary executions that followed it.

The evacuations that followed might have gone smoothly if not for the influence of one of Bashar al-Assad’s foreign backers: the Islamic Republic of Iran. Notwithstanding reports of the Assad regime’s murders of civilians after the capture of the city, the government did seem prepared to accept the terms of the ceasefire as they were initially defined.

Meanwhile, Assad’s supporters in Moscow provided public guarantees that a humanitarian corridor would remain open for the removal of Aleppo residents to areas that remain under rebel control.

But Tehran was evidently unwilling to accept this. The Islamic Republic quickly tried to act unilaterally to gain additional concessions from the Syrian rebels and the international community. And it followed up with action, stopping 1,000 evacuees at an Iranian militant checkpoint, even after those civilians had already passed a Russian checkpoint closer to the besieged city.

All of this was foreseeable. Iran has been the greatest impediment to peace virtually since the beginning of the Syrian Civil War in 2011. Its efforts to stand in the way of basic humanitarian work in Aleppo are perfectly in keeping with the Iranian leadership’s behaviour both at home and within its foreign sphere of influence.

These developments are perhaps the clearest pieces of evidence yet for the conclusion that peace in Syria is impossible as long as Iran continues to play a leading role there. Surely this was obvious to the international community months or even years ago. Though the United Nations was too weak to do anything about it, the United States and Europe were, predictably, unwilling to take their own actions to constrain Iran. The unimaginable loss of life and property in Aleppo is the consequence of that inaction, and Iran’s current behaviour makes it clear that the consequences will continue to accrue for as long as the international community allows Tehran to dictate the course of events in Syria.

The sad fact is that Western powers did more than just refuse to stand in Iran’s way as it wielded more and more influence over the Assad government and its wartime activities. The West actually granted Iran a place at the negotiating table, despite the well-justified objections of some within Middle East and other long-standing opponents of the Iranian regime.

The main Iranian resistance group, the People’s Mojahedin Organization of Iran (PMOI/MEK), has been trying for years to bring Western attention to the destructive role that Iran has been playing in Syria and throughout the region.

Now, in light of recent events, one might argue that the role changes slightly for this and other advocates of the Syrian opposition. Instead of simply highlighting the danger that Tehran poses to civilians throughout the Middle East, these groups must make it clear to global policy makers that their hands-off approach to the Islamic Republic of Iran has helped to create the conditions that allowed the vast amounts of destruction that we have witnessed in recent days.

Indeed, in a statement following the fall of Aleppo, Iranian Resistance leader Maryam Rajavi appealed to the international community, saying, “The regime in Tehran is the source of crisis in the region and killings in Syria” and “peace and tranquillity… can only be achieved by evicting this regime from the region.”

Surely the Western world should not need to be told this. Our policy makers were there each time a ceasefire was negotiated, only to be violated by Iran-backed Shiite militants. They were there every time a prospective political solution failed because of the absolute intransigence of the Iranian theocracy. The aftermath of the Battle of Aleppo only serves to reiterate that Iran will never accept a negotiated political solution; that it will never accept anything less than the total destruction of the Syrian opposition irrespective of any humanitarian catastrophe that entails.

Beyond that, Western policy makers have been there or thereabouts to witness, virtually at first hand, Tehran’s behaviour throughout the history of the Islamic Republic – with its double-dealing and broken promises; its use of torture and arbitrary violence; its hostage taking. Yet, shamelessly, our Governments still, vis-à-vis the 1988 Iranian massacre, quibble over the detail. Little wonder these awful tactics are able to be promoted in Syria by the Iranian regime, which is now effectively treating the civilians of Aleppo as hostages to be bartered for more conciliation and concessions from the international community.

One must ask whether the UK and the US have the leadership, moral and strategic, to take immediate steps to halt Iran’s destructive meddling. If what we see in Aleppo is bad be assured Iranian regime’s role in Syria, can only get worse. And who except ourselves do we have to blame?